1. Field
Apparatuses consistent with exemplary embodiments relate to an image forming apparatus, a microcontroller, and methods for controlling the image forming apparatus and the microcontroller, and more particularly, to an image forming apparatus which can realize a low power mode, a microcontroller, and methods for controlling the image forming apparatus and the microcontroller.
2. Description of the Related Art
Demands for low power of all types of electronic products have been reinforced. Therefore, if electronic products do not meet these demands, the electronic products cannot be sold due to regulations in spite of their high performances and competitive prices.
Current specifications of the Energy Star Program require that power between 1 W and 2 W should be consumed in a standby mode according to types of apparatuses. From now on, the Energy Star Program will require power consumption of 1 W or less even in a standby state in which a network service is possible. Therefore, all electronic companies mobilize several methods to achieve this requirement.
Also, consumers should not feel use inconveniences according to whether apparatuses are in a low power state or a normal operation state. This will be a core of competitiveness between technologies of apparatuses.
In order to achieve a low power standby mode, most companies access the following method. In other words, a main central processing unit (CPU) having a high performance and an auxiliary CPU consuming low power are constituted. A service is provided through the main CPU in a normal mode, when a system enters a standby mode due to a specific condition, the main CPU and an unnecessary system are powered off through the auxiliary CPU, and a service request is monitored through the auxiliary CPU. Also, when a user request a service, the auxiliary CPU applies power to the main CPU and auxiliary circuits to provide the service. In other words, a CPU of a small gate size is added besides existing CPU cores.
For example, a conventional system includes a main controller and a sub-controller which recognizes 10 receiving and wakeup processing events in a low power mode to apply power to the main controller. In this case, prices increase due to the installation of an additional chip, and additional circuit and software for communications between the main controller and the sub controller are required.
As another example, CPUs of a main controller and a sub controller are integrated into a System-on-chip (SOC). Also, the main controller controls Micro Channel Architecture (MAC), a universal serial bus (USB), a Fax, an input/output (I/O) port, etc. in a service mode, and the sub controller processes data of the MAC, the USB, the Fax, the I/O port, etc. in a low power mode. Even in this case, an additional CPU for low power is to be installed.
In order to achieve low power, power domains of internal modules are separated from one another to control in order to power on/off a particular block and power off an unused block. In particular, except for a sub controller and apparatuses for receiving events, other apparatuses are powered off.
However, reducing standby power by using this method reaches the limit. Therefore, an object for realizing low power has gradually extended from a controller to a peripheral connection apparatus. Besides a self refresh mode, there are various methods for realizing low power of a double data rate (DDR) memory that is a representative peripheral device. For example, there is a method for controlling to power off a pad of a DDR memory in a sleep mode.
In this case, instead of changing an existing system, a pad control circuit of a DDR memory is installed in the existing system to replace only a memory in order to achieve low power to some degree. However, in terms of a whole system, a pad of a C controller controlling the DDR memory cannot be controlled. Therefore, power loss occurring in that part cannot be prevented.
Also, if an interface unit is powered off in a low power mode, an occurrence of a particular event for changing a low power mode such as a self refresh mode to a normal mode interrupts smooth data communications. As a result, malfunctioning (data loss) may occur.